An electric power meter is adapted to measure the power consumption of electric loads connected to a power supply line. The power meter is coupled to the supply line and measures the voltage at the supply line and the current flowing through the supply line in order to determine the power consumption.
A conventional electromechanical power meter includes a non-electronic display that displays the power that has been consumed since the power meter has been installed. An employee of the utility company regularly (usually a few times each year) evaluates the meter reading in order to calculate the power consumption since the last evaluation and in order to bill the customer accordingly.
A smart electric power meter is an electronic device that is coupled to the power line and that is adapted to measure the power consumption and to store a measurement value representing the power consumption in a memory device. The memory can be read out on-site. Alternatively, the smart meter may have an interface which connects the smart meter to a communication network. Via the network the utility company can read the memory so that there is no need to have an employee on-site. The network can be any suitable network, like a wireless network, a telephone network, or a power line.
Power consumption data, especially when they are transmitted to the utility company, are sensitive data, because they allow conclusions to be drawn based on the consumer's habits and could, therefore, be abusively used for surveillance purposes by unauthorized third parties that may “eavesdrop” on the network. In addition, power consumption data may be tampered with by the consumer in order to reduce electricity bills.
Some smart power meters include a switching arrangement (circuit breaker) which can be remotely operated by the utility company in order to interrupt the power supply when, for example, the customer does not pay the bill or is consuming an excess of power. It goes without saying that unauthorized operation of the circuit breaker may have severe consequences for the consumer, but also on the stability of the grid.